The present invention relates to metal-refining ferroalloy to be added to molten steels, particularly to killed steel, for the purpose of deoxidizing the steel and adjusting the composition thereof.
Aluminum has been widely used as deoxidizer and grain-size controller in the manufacture of steels, particularly killed steel, by the hot-metal process. In the conventional method, aluminum is added to the molten steel by throwing small solid masses of aluminum into the molten steel bath. Such addition suffers, however, from the disadvantage that, because of the lower specific gravity of aluminum than molten steel and the high reactivity of aluminum with molten steel, the masses of aluminum cannot penetrate into the molten steel with sufficient depth so that the yield of aluminum addition is not only poor but is wide and unpredictable variation. The term "yield of aluminum addition" as used herein means a ratio of the amount of aluminum contained in a product to that added to molten steel.
A method has been proposed for improving and stabilizing the yield of aluminum addition, in which aluminum is added to molten steel by shooting aluminum shaped in the form of cannon balls into the bath at a high speed. It is difficult, however, by this method to accomplish rapid addition of a large amount of aluminum because of the limited capacity of the shooter.